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gman89 02-24-2011 05:51 AM

Theoretical resources difficult to find
 
Hi,

I'm a mechanical engineer intending to do my thesis on some aspect of gunsmithing (I work for a small defense firm so I have some resources at my disposal to do this). The problem is that getting extensive resources, namely books, on INDIVIDUAL topics is difficult to find.

I am leaning towards doing a topic on harmonic distortion of barrels, and how to to improve accuracy by mitigating this effect. However, I can't seem to find more than a few paragraphs at a time. Does anyone know of any books that are quite scientific and extensive enough for what I'm attempting?

In addition, it would be awesome to hear if people like you who are more experienced than me at this point have any good ideas for a possible topic. But my main intention is to obtain resources.

Any help would be appreciated.

c3shooter 02-24-2011 11:47 AM

Would suggest that you try contacting some of the firearms makers- Remington would be my first shot (pun intended), along with Barrett, and some of the first class barrel makers. I am certain that somewhere out there a published thesis titled "Calculating and controlling natural harmonic frequencies in ordnance steel constructions" but I do not know where it is. But the folks I mentioned may have been the writer's of such a thesis, or provided the data used for it. Good luck.

PS- secret of accuracy may not be in the ELIMINATION of distortion, but in STANDARDIZING distortion. Who cares if it is off, so long as the amount of off is uniform and repeatable?

PPS- also check some of the Applied Physics labs. Johns Hopkins and SRI are two that come to mind. Over the years, they have done some rather esoteric research on firearms.

gman89 02-25-2011 05:50 AM

I guess I should search for something that is more broad like the example you mentioned. The science behind it is not so unique that a more generalized book won't have enough information.

Could anyone describe the nature of the vibration and the general process involved? I was speaking to someone else and they mentioned that they believe there are non-linearities involved because it's not a steady state vibrational system. If I had some more details like this I might be able to search for something that doesn't have the term "firearm" or "barrel" in the title.

Ruzai 02-25-2011 07:43 AM

This simply reminds me of a few videos on Youtube of slow motion capture of barrel flex on guns like the AK-47 where it's apparent. Honestly I cant account for much understanding beyond what happens in a barrel and how un-uniform harmonics affect accuracy at distance. Anyhow, here's the video just so others that might be looking in the thread might get an idea of what you fellas are discussing. Good luck on your search Gman89.

rifleman55 03-05-2011 05:44 PM

The harmonics are different with every rifle.
As was said, the idea is to get the barrel to move as far as the harmonics are concerned the same way every time. There are tuners, put on the end of the barrel, adjustable to change the weight and the way the barrel moves. Tuners put on the middle part of the barrel.
Look up Rimfireaccuracy site, there is a lot of talk about barrels and the harmonics there.

Call Shilen barrels, the guy that owns the company will most likely talk to you about it. He's a custom barrel manufactuer.

Barrel harmonics is an inexact science, we know that every barrel has it's own harmonics and has to be tuned for the best accuracy. In other words, if it whips upward, it needs to whip upward the same for every shot. Change anything, bullet, bullet weight, the way the rifle is held and you will change the harmonics and need to start over.
The heavier the barrel, the less movement, but every barrel has harmonics.
Go to www.brownells.com, they have a book by a guy named Pope, he was one of the best barrel makers ever. He is long gone, but the book should contain a lot of info. Also get "Understanding Firearms Ballistics" by Robert Rinker. There are things about barrels in the book and you need to understand ballistics to help understand what barrels do. This book will help. Easy to read, some math you can work out. If you have trouble find them on the web site, call, they will find it for you. If they don't have the books, go to www.midwayusa.com

I'm a retired Gunsmith and have had to try everything to get the harmonics right on some guns. Each is different. It's not easy and requires a lot of expermintation and a lot of shot ammo sometimes to get it right. Most people don't get into this extream accuracy except for comp shooters. They have and will try anything if it's within the rules and makes their rifles shoot better.
Just getting an adjustable tuner perfect can use 500 rounds of ammo sometimes. You picked an interesting subject. The two books I suggested should help. I have not read the book by Pope, but it should give some more understanding.

Also, not every barrel whips like the AK-47, it is the extream rifle for barrel whip.

Good luck, John K


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